tock-mirror/transformations/SimplifyExprs.hs
Neil Brown 8f767ff0d4 Made all the imports of Data.Generics have an import list
This makes sure that we catch all leftover instances of using SYB to do generic operations that we should be using Polyplate for instead.  Most modules should only import Data, and possibly Typeable.
2009-04-09 15:36:37 +00:00

596 lines
26 KiB
Haskell

{-
Tock: a compiler for parallel languages
Copyright (C) 2007, 2008 University of Kent
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 2 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program. If not, see <http://www.gnu.org/licenses/>.
-}
-- | Simplify expressions in the AST.
module SimplifyExprs where
import Control.Monad.State
import Data.Generics (Data)
import qualified Data.Map as Map
import qualified AST as A
import CompState
import Errors
import EvalConstants
import Metadata
import Pass
import qualified Properties as Prop
import ShowCode
import Traversal
import Types
import Utils
simplifyExprs :: [Pass A.AST]
simplifyExprs =
[ functionsToProcs
, removeAfter
, expandArrayLiterals
, pullRepCounts
, pullUp False
, transformConstr
]
-- These are a special case, and do not get pulled up, nor turned into PROCs:
builtInOperatorFunction :: A.Name -> Bool
builtInOperatorFunction = (`elem` occamBuiltInOperatorFunctions) . A.nameName
-- | Convert FUNCTION declarations to PROCs.
functionsToProcs :: PassOn A.Specification
functionsToProcs = pass "Convert FUNCTIONs to PROCs"
(Prop.agg_namesDone ++ [Prop.expressionTypesChecked, Prop.parUsageChecked,
Prop.functionTypesChecked])
[Prop.functionsRemoved]
(applyBottomUpM doSpecification)
where
doSpecification :: A.Specification -> PassM A.Specification
doSpecification (A.Specification m n (A.Function mf smrm rts fs evp))
| not (builtInOperatorFunction n)
= do -- Create new names for the return values.
specs <- sequence [makeNonceVariable "return_formal" mf t A.Abbrev | t <- rts]
let names = [n | A.Specification mf n _ <- specs]
-- Note the return types so we can fix calls later.
modify $ (\ps -> ps { csFunctionReturns = Map.insert (A.nameName n) rts (csFunctionReturns ps) })
-- Turn the value process into an assignment process.
let p = fmap (vpToSeq m n [A.Variable mf n | n <- names]) evp
let st = A.Proc mf smrm (fs ++ [A.Formal A.Abbrev t n | (t, n) <- zip rts names]) p
-- Build a new specification and redefine the function.
let spec = A.Specification m n st
let nd = A.NameDef {
A.ndMeta = mf,
A.ndName = A.nameName n,
A.ndOrigName = A.nameName n,
A.ndSpecType = st,
A.ndAbbrevMode = A.Original,
A.ndNameSource = A.NameUser,
A.ndPlacement = A.Unplaced
}
defineName n nd
return spec
doSpecification s = return s
vpToSeq :: Meta -> A.Name -> [A.Variable] -> Either (A.Structured A.ExpressionList) A.Process -> A.Process
vpToSeq m n vs (Left el) = A.Seq m $ vpToSeq' el vs
vpToSeq _ n vs (Right p) = applyBottomUp doAssignSubst p
where
doAssignSubst :: A.Process -> A.Process
doAssignSubst ass@(A.Assign m [A.Variable _ dest] el) = if (A.nameName dest == A.nameName n) then (A.Assign m vs el) else ass
doAssignSubst p = p
vpToSeq' :: A.Structured A.ExpressionList -> [A.Variable] -> A.Structured A.Process
vpToSeq' (A.Spec m spec s) vs = A.Spec m spec (vpToSeq' s vs)
vpToSeq' (A.ProcThen m p s) vs = A.ProcThen m p (vpToSeq' s vs)
vpToSeq' (A.Only m el) vs = A.Only m $ A.Assign m vs el
-- | Convert AFTER expressions to the equivalent using MINUS (which is how the
-- occam 3 manual defines AFTER).
removeAfter :: PassOn2 A.Expression A.ExpressionList
removeAfter = pass "Convert AFTER to MINUS"
[Prop.expressionTypesChecked]
[Prop.afterRemoved]
(applyBottomUpM2 doExpression doExpressionList)
where
doFunctionCall :: (Meta -> A.Name -> [A.Expression] -> a)
-> Meta -> A.Name -> [A.Expression] -> PassM a
doFunctionCall f m n args
= do mOp <- builtInOperator n
ts <- mapM astTypeOf args
let op s = A.Name (A.nameMeta n) $ occamDefaultOperator s ts
case mOp of
Just "AFTER"
| A.nameName n == occamDefaultOperator "AFTER" [A.Byte, A.Byte] ->
let one = A.Literal m A.Byte $ A.IntLiteral m "1"
oneTwoSeven = A.Literal m A.Byte $ A.IntLiteral m "127"
in return $ f m (op "<")
[A.FunctionCall m (op "MINUS")
[A.FunctionCall m (op "MINUS") args
, one]
,oneTwoSeven]
| otherwise
-> let zero = A.Literal m (head ts) $ A.IntLiteral m "0"
in return $ f m (op ">") [A.FunctionCall m (op "MINUS") args, zero]
_ -> return $ f m n args
doExpression :: A.Expression -> PassM A.Expression
doExpression e@(A.FunctionCall m n args)
= doFunctionCall A.FunctionCall m n args
doExpression e = return e
doExpressionList :: A.ExpressionList -> PassM A.ExpressionList
doExpressionList e@(A.FunctionCallList m n args)
= doFunctionCall A.FunctionCallList m n args
doExpressionList e = return e
-- | For array literals that include other arrays, burst them into their
-- elements.
expandArrayLiterals :: PassOn (A.Structured A.Expression)
expandArrayLiterals = pass "Expand array literals"
[Prop.expressionTypesChecked, Prop.processTypesChecked]
[Prop.arrayLiteralsExpanded]
(applyBottomUpM doArrayElem)
where
doArrayElem :: A.Structured A.Expression -> PassM (A.Structured A.Expression)
doArrayElem ae@(A.Only _ e)
= do t <- astTypeOf e
case (t, e) of
(A.Array ds _, _) -> expand ds e
_ -> return ae
doArrayElem ae = return ae
expand :: [A.Dimension] -> A.Expression -> PassM (A.Structured A.Expression)
expand [] e = return $ A.Only (findMeta e) e
expand (A.UnknownDimension:_) e
= dieP (findMeta e) "array literal containing non-literal array of unknown size"
expand (A.Dimension n:ds) e
= do -- Because it's an array literal, we must know the size.
size <- evalIntExpression n
elems <- sequence [case e of
A.Literal _ _ (A.ArrayListLiteral _ (A.Several _ ls)) ->
return $ ls !! i
_ -> expand ds (A.SubscriptedExpr m
(A.Subscript m A.NoCheck $
makeConstant m i) e)
| i <- [0 .. size - 1]]
return $ A.Several (findMeta e) elems
where m = findMeta e
-- | We pull up the loop (Rep) counts into a temporary expression, whenever the loop
-- count could be modified within the loop. Here are all things that can be replicated:
-- SEQ -- can be altered during the loop, must pull up
-- PAR -- count cannot be modified by code inside the loop (it is used before any PAR branches are run)
-- BUT since we implement replicated pars using a loop that forks off those
-- processes, it seems safest to pull up
-- IF -- cannot be altered during loop; once body executes, loop is effectively broken
-- ALT -- same as IF
-- BUT the programmer could offer to read into the replication count, which
-- could cause all sorts of horrendous problems, so pull up
-- Therefore, we only need to pull up the counts for SEQ, PAR and ALT
--
-- TODO for simplification, we could avoid pulling up replication counts that are known to be constants
--
-- TODO we should also pull up the step counts
pullRepCounts :: PassOn A.Process
pullRepCounts = pass "Pull up replicator counts for SEQs, PARs and ALTs"
(Prop.agg_namesDone ++ Prop.agg_typesDone)
[]
(applyBottomUpM pullRepCountProc)
where
pullRepCountStr :: Data a => Bool -> A.Structured a
-> StateT (A.Structured A.Process -> A.Structured A.Process)
PassM (A.Structured a)
pullRepCountStr addHere (A.Spec m (A.Specification mspec n (A.Rep mrep (A.For mfor
from for step))) scope)
= do t <- lift $ astTypeOf for
spec@(A.Specification _ nonceName _) <- lift $ makeNonceIsExpr "rep_for" mspec t for
let newRepSpec = (A.Rep mrep (A.For mfor from (A.ExprVariable mspec $ A.Variable mspec nonceName) step))
lift $ modifyName n $ \nd -> nd { A.ndSpecType = newRepSpec }
if addHere
then return $ A.Spec mspec spec $
A.Spec m (A.Specification mspec n newRepSpec) scope
else do modify (. A.Spec mspec spec)
return $ A.Spec m (A.Specification mspec n newRepSpec) scope
pullRepCountStr _ s = return s
pullRepCountProc :: Transform A.Process
pullRepCountProc (A.Alt m p body) = evalStateT (pullRepCountStr True body) id >>* A.Alt m p
pullRepCountProc (A.Seq m body) = evalStateT (pullRepCountStr True body) id >>* A.Seq m
pullRepCountProc (A.Par m p body)
= do (body', spec) <- runStateT (pullRepCountStr False body) id
return $ A.Seq m $ spec $ A.Only m $ A.Par m p body'
pullRepCountProc p = return p
transformConstr :: PassOnOps (ExtOpMSP BaseOp)
transformConstr = pass "Transform array constructors into initialisation code"
(Prop.agg_namesDone ++ Prop.agg_typesDone ++ [Prop.subscriptsPulledUp])
[Prop.arrayConstructorsRemoved]
(applyBottomUpMS doStructured)
where
-- For arrays, this takes a constructor expression:
-- VAL type name IS [i = rep | expr]:
-- ...
-- and produces this:
-- type name:
-- PROCTHEN
-- INT indexvar:
-- SEQ
-- indexvar := 0
-- SEQ i = rep
-- SEQ
-- name[indexvar] := expr
-- indexvar := indexvar + 1
-- ...
--
-- For lists, it takes the similar expression and produces:
-- type name:
-- PROCTHEN
-- SEQ i = rep
-- name += [expr]
doStructured :: Data a => A.Structured a -> PassM (A.Structured a)
doStructured (A.Spec m (A.Specification m' n (A.Is _ _ _
(A.ActualExpression expr@(A.Literal m'' t (A.ArrayListLiteral _ (A.Spec _ (A.Specification _
repn (A.Rep _ rep)) repExp)))))) scope)
= do case t of
A.Array {} ->
do indexVarSpec@(A.Specification _ indexName _) <- makeNonceVariable "array_constr_index" m'' A.Int A.Original
let indexVar = A.Variable m'' indexName
(repExp', specs) = stripSpecs repExp
tInner <- trivialSubscriptType m t
-- To avoid confusion in later passes, we must change the abbreviation
-- mode for this thing from ValAbbrev (which it must have been)
-- to Original, since we are now actually declaring it and assigning
-- to it:
modifyName n $ \nd -> nd {A.ndAbbrevMode = A.Original}
incIndex <- incrementIndex indexVar
let body = specs $ A.Several m''
[ assignItem tInner indexVar repExp'
, incIndex ]
body' <- applyBottomUpMS doStructured body
return $ declDest $ A.ProcThen m''
(A.Seq m'' $ A.Spec m'' indexVarSpec $
A.Several m'' [assignIndex0 indexVar,
replicateCode $ body'
])
scope
A.List {} ->
return $ declDest $ A.ProcThen m''
(A.Seq m'' $ replicateCode $ appendItem)
scope
_ -> diePC m $ formatCode "Unsupported type for array constructor: %" t
where
-- Also strips ProcThen
stripSpecs :: A.Structured A.Expression -> (A.Structured A.Expression,
A.Structured A.Process -> A.Structured A.Process)
stripSpecs (A.Spec m spec scope)
= let (result, innerSpecs) = stripSpecs scope in
(result, A.Spec m spec . innerSpecs)
stripSpecs (A.ProcThen m proc body)
= let (result, innerSpecs) = stripSpecs body in
(result, A.ProcThen m proc . innerSpecs)
stripSpecs se = (se, id)
declDest :: Data a => A.Structured a -> A.Structured a
declDest = A.Spec m (A.Specification m' n (A.Declaration m' t))
assignIndex0 :: A.Variable -> A.Structured A.Process
assignIndex0 indexVar = A.Only m'' $ A.Assign m'' [indexVar] $
A.ExpressionList m'' [A.Literal m'' A.Int $ A.IntLiteral m'' "0"]
incrementIndex :: A.Variable -> PassM (A.Structured A.Process)
incrementIndex indexVar
= do indexVar_plus1 <- addOne $ A.ExprVariable m'' indexVar
return $ A.Only m'' $ A.Assign m'' [indexVar] $ A.ExpressionList m'' [indexVar_plus1]
assignItem :: A.Type -> A.Variable -> A.Structured A.Expression -> A.Structured A.Process
assignItem t' indexVar repExp' = A.Only m'' $ A.Assign m'' [A.SubscriptedVariable m''
(A.Subscript m'' A.NoCheck $ A.ExprVariable m'' indexVar) $
A.Variable m'' n] $ A.ExpressionList m'' [
case repExp' of
A.Only _ e -> e
_ -> A.Literal m'' t' $ A.ArrayListLiteral m'' repExp'
]
appendItem :: A.Structured A.Process
appendItem = A.Only m'' $ A.Assign m'' [A.Variable m'' n] $
A.ExpressionList m'' [A.FunctionCall m'' (A.Name m'' "++")
[A.ExprVariable m'' $ A.Variable m'' n
,A.Literal m'' (let A.List tInner = t in tInner) $ A.ArrayListLiteral m'' repExp
]]
replicateCode :: Data a => A.Structured a -> A.Structured a
replicateCode = A.Spec m'' (A.Specification m'' repn (A.Rep m'' rep))
doStructured s = return s
type PullUpOps = ExtOpMSP BaseOp
`ExtOpMP` A.Process
`ExtOpMP` A.Structured A.Expression
`ExtOpMP` A.Specification
`ExtOpMP` A.LiteralRepr
`ExtOpMP` A.Expression
`ExtOpMP` A.Variable
`ExtOpMP` A.ExpressionList
-- | Find things that need to be moved up to their enclosing Structured, and do
-- so.
pullUp :: Bool -> PassOnOps PullUpOps
pullUp pullUpArraysInsideRecords = pass "Pull up definitions"
(Prop.agg_namesDone ++ Prop.agg_typesDone ++ [Prop.functionsRemoved, Prop.seqInputsFlattened])
[Prop.functionCallsRemoved, Prop.subscriptsPulledUp]
recurse
where
ops :: PullUpOps
ops = baseOp
`extOpMS` (ops, doStructured)
`extOpM` doProcess
`extOpM` doRepArray
`extOpM` doSpecification
`extOpM` doLiteralRepr
`extOpM` doExpression
`extOpM` doVariable
`extOpM` doExpressionList
recurse :: RecurseM PassM PullUpOps
recurse = makeRecurseM ops
descend :: DescendM PassM PullUpOps
descend = makeDescendM ops
-- | When we encounter a Structured, create a new pulled items state,
-- recurse over it, then apply whatever pulled items we found to it.
doStructured :: TransformStructured PullUpOps
doStructured s
= do pushPullContext
-- Recurse over the body, then apply the pulled items to it
s' <- descend s >>= applyPulled
-- ... and restore the original pulled items
popPullContext
return s'
doProcActual :: Transform A.Actual
doProcActual a@(A.ActualVariable {}) = descend a
doProcActual a@(A.ActualExpression {}) = descend a
-- Definitely pull up channel arrays and claims:
doProcActual a
= do a' <- recurse a
t <- astTypeOf a
spec@(A.Specification _ n' _)
<- defineNonce m "actual" (A.Is m A.Abbrev t a) A.Abbrev
addPulled (m, Left spec)
return $ A.ActualVariable (A.Variable m n')
where
m = findMeta a
-- | As with doStructured: when we find a process, create a new pulled items
-- context, and if we find any items apply them to it.
doProcess :: A.Process -> PassM A.Process
doProcess p
= do pushPullContext
p' <- case p of
A.ProcCall m n as
-> mapM doProcActual as >>* A.ProcCall m n
_ -> descend p
pulled <- havePulled
p'' <- if pulled
then liftM (A.Seq emptyMeta) $ applyPulled (A.Only emptyMeta p')
else return p'
popPullContext
return p''
-- | There are issues with array constructors. Consider:
-- [i = 0 FOR 10 | [i, i+1]]
-- You cannot pull the inner array literal up past the replicator,
-- because then i will not be in scope. So what we must do is
-- pull the array up to just inside the replicator (while pulling the whole
-- literal up as normal):
-- VAL array_expr_outer IS [i = 3 FOR 5 |
-- VAL array_expr_inner IS [i, i + 1]:
-- array_expr_inner]
-- Then when it is transformed later, it should become:
-- array_expr_outer:
-- PROCTHEN
-- INT array_constr_index:
-- SEQ
-- array_constr_index := 0
-- SEQ i = 3 FOR 5
-- VAL array_expr_inner IS [i, i + 1]:
-- SEQ
-- array_expr_outer[array_constr_index] := array_expr_inner -- itself flattened later!
-- array_constr_index := array_constr_index + 1
doRepArray :: A.Structured A.Expression -> PassM (A.Structured A.Expression)
doRepArray (A.Spec m spec@(A.Specification _ _ (A.Rep {})) scope)
= do -- We descend into the spec before we push a new context,
-- as anything in the spec should be pulled up to the outer context,
-- not inside the replicator
spec' <- descend spec
pushPullContext
scope' <- recurse scope >>= applyPulled
popPullContext
return $ A.Spec m spec' scope'
doRepArray s = descend s
-- | Filter what can be pulled in Specifications.
doSpecification :: A.Specification -> PassM A.Specification
-- Iss might be SubscriptedVars -- which is fine; the backend can deal with that.
doSpecification (A.Specification m n (A.Is m' am t (A.ActualVariable v)))
= do v' <- descend v -- note descend rather than pullUp
return $ A.Specification m n (A.Is m' am t $ A.ActualVariable v')
-- IsExprs might be SubscriptedExprs, and if so we have to convert them.
doSpecification (A.Specification m n (A.Is m' am t (A.ActualExpression e)))
= do e' <- doExpression' e -- note doExpression' rather than recurse
return $ A.Specification m n (A.Is m' am t $ A.ActualExpression e')
-- Convert RetypesExpr into Retypes of a variable.
doSpecification (A.Specification m n (A.RetypesExpr m' am toT e))
= do e' <- doExpression e
fromT <- astTypeOf e'
spec@(A.Specification _ n' _) <- makeNonceIsExpr "retypes_expr" m' fromT e'
addPulled $ (m', Left spec)
return $ A.Specification m n (A.Retypes m' am toT (A.Variable m' n'))
doSpecification s = descend s
-- | Filter what can be pulled in LiteralReprs.
doLiteralRepr :: A.LiteralRepr -> PassM A.LiteralRepr
-- FIXME: We could do away with ArrayElem and have a rule like the below
-- for nested array literals.
-- Don't pull up array expressions that are fields of record literals.
doLiteralRepr (A.RecordLiteral m es)
= do es' <- mapM (if pullUpArraysInsideRecords then doExpression else doExpression') es -- note doExpression' rather than recurse
return $ A.RecordLiteral m es'
doLiteralRepr lr = descend lr
-- | Pull array expressions that aren't already non-subscripted variables.
-- Also pull lists that are literals or constructed
doExpression :: A.Expression -> PassM A.Expression
-- For is-defined, we don't want to pull up:
doExpression e@(A.IsDefined {}) = return e
doExpression e
-- This part handles recursing into the expression first:
= do e' <- doExpression' e
t <- astTypeOf e'
case t of
A.Array _ _ ->
case e' of
A.ExprVariable _ (A.Variable _ _) -> return e'
A.ExprVariable _ (A.DirectedVariable _ _ _) -> return e'
--TODO work out whether to pull up DerefVariable
_ -> pull t e'
A.List _ ->
case e' of
A.Literal {} -> pull t e'
_ -> return e'
A.Record _ ->
case e' of
A.Literal {} -> pull t e'
_ -> return e'
_ -> return e'
where
pull :: A.Type -> A.Expression -> PassM A.Expression
pull t e
= do let m = findMeta e
spec@(A.Specification _ n _) <- makeNonceIsExpr "array_expr" m t e
addPulled $ (m, Left spec)
return $ A.ExprVariable m (A.Variable m n)
-- | Pull any variable subscript that results in an array, or contains a slice.
doVariable :: A.Variable -> PassM A.Variable
doVariable v@(A.SubscriptedVariable m sub _)
= do v' <- if isSlice sub then descend v else descendAfterSubscripts v
t <- astTypeOf v'
case t of
A.Array _ _ ->
do origAM <- abbrevModeOfVariable v'
let am = makeAbbrevAM origAM
spec@(A.Specification _ n _) <- makeNonceIs "array_slice" m t am v'
addPulled $ (m, Left spec)
return $ A.Variable m n
_ -> return v'
where
descendAfterSubscripts (A.SubscriptedVariable m sub v) | not (isSlice sub)
= do sub' <- recurse sub
v' <- descendAfterSubscripts v
return $ A.SubscriptedVariable m sub' v'
descendAfterSubscripts v = doVariable v
isSlice (A.SubscriptFromFor {}) = True
isSlice (A.SubscriptFrom {}) = True
isSlice (A.SubscriptFor {}) = True
isSlice _ = False
doVariable v@(A.DirectedVariable m dir innerV)
= do t <- astTypeOf innerV
case t of
A.Array ds (A.Chan attr innerT) ->
do let ds' = [case d of
A.Dimension {} -> d
A.UnknownDimension -> A.Dimension $ A.ExprVariable m $
specificDimSize i innerV
| (d, i) <- zip ds [0..]]
spec@(A.Specification _ n _) <- makeNonceIs "dir_array" m
(A.Array ds' $ A.ChanEnd dir (dirAttr dir attr) innerT) A.Abbrev v
addPulled $ (m, Left spec)
return $ A.Variable m n
_ -> descend v
doVariable v@(A.DerefVariable m innerV)
= do t <- astTypeOf v
case t of
A.Array ds innerT ->
do let ds' = [case d of
A.Dimension {} -> d
A.UnknownDimension -> A.Dimension $ A.ExprVariable m $
specificDimSize i innerV
| (d, i) <- zip ds [0..]]
spec@(A.Specification _ n _) <- makeNonceIs "mob_array" m
(A.Array ds' innerT) A.Abbrev v
addPulled $ (m, Left spec)
return $ A.Variable m n
_ -> descend v
doVariable v@(A.VariableSizes m _)
= do v' <- descend v
t <- astTypeOf v'
spec@(A.Specification _ n _) <- makeNonceIs "sizes_array" m t A.ValAbbrev v'
addPulled $ (m, Left spec)
return $ A.Variable m n
doVariable v = descend v
-- | Convert a FUNCTION call into some variables and a PROC call.
convertFuncCall :: Meta -> A.Name -> [A.Expression] -> PassM [A.Variable]
convertFuncCall m n es
= do es' <- recurse es
ets <- sequence [astTypeOf e | e <- es']
ps <- get
rts <- case Map.lookup (A.nameName n) (csFunctionReturns ps) of
Nothing -> dieP m "Could not find function returns"
Just x -> return x
specs <- sequence [makeNonceVariable "return_actual" m t A.Original | t <- rts]
sequence_ [addPulled $ (m, Left spec) | spec <- specs]
let names = [n | A.Specification _ n _ <- specs]
let vars = [A.Variable m n | n <- names]
let call = A.ProcCall m n (map A.ActualExpression es' ++ map A.ActualVariable vars)
addPulled $ (m, Right call)
return vars
doExpression' :: A.Expression -> PassM A.Expression
-- Convert single-valued function calls.
doExpression' (A.FunctionCall m n es) | not $ builtInOperatorFunction n
= do [v] <- convertFuncCall m n es
return $ A.ExprVariable m v
-- Convert SubscriptedExprs into SubscriptedVariables.
doExpression' (A.SubscriptedExpr m s e)
= do e' <- recurse e
s' <- recurse s
t <- astTypeOf e'
spec@(A.Specification _ n _) <- makeNonceIsExpr "subscripted_expr" m t e'
addPulled $ (m, Left spec)
return $ A.ExprVariable m (A.SubscriptedVariable m s' (A.Variable m n))
doExpression' e = descend e
doExpressionList :: A.ExpressionList -> PassM A.ExpressionList
-- Convert multi-valued function calls.
doExpressionList (A.FunctionCallList m n es)
| not (builtInOperatorFunction n)
= do vs <- convertFuncCall m n es
return $ A.ExpressionList m [A.ExprVariable m v | v <- vs]
doExpressionList el = descend el